Electronic printers, as described, for example, by documents U.S. Pat. No. 4,949,283, U.S. Pat. No. 5,634,730, PCT/SE01/01575, and PCT/AU03/00168, are already known.
From a general point of view, said electronic printers have in common a print head operable by a manual print control on a medium to be printed, an external housing being comfortable for a hand gripping, communication means for coupling the print head with an electronic apparatus such as a computer, and position detecting means adapted to detect the position of the print head.
The above mentioned printers are rough in the movement and positioning of the print head. Further, they require a manual operation by a user that moves the print head on the medium to be printed by pressing the print control.
In order to better illustrate the background of art, U.S. Pat. No. 5,634,730 is particularly considered, which discloses a hand-held electronic printer having a housing that can be manually positioned on a surface of the medium to be printed and remain stationary during a print sequence. The housing has an aperture that generally defines a printing area on the medium. A printing device is disposed in the housing and comprises a print head that, under the control of an actuator, is moved from an initial position to a final position to perform the printing operation. A spring is operatively connected to the print head to return the same to the initial position. Electronic control means are disposed in the housing to synchronise the printing in relation with the movements of the print head.
In the specification of U.S. Pat. No. 5,634,730 it is often said that its object is to make the electronic printer similar to a conventional mechanical stamper, in which the rubber marker is manually lowered in vertical direction up to the surface of the medium to leave a desired mark. However, the printer according to U.S. Pat. No. 5,634,730 does not perform really the operation of a traditional stamper, since the force that is exerted by the user on the actuator does not bring the print head near to the medium, as the print head is always close to the medium, but it produces an horizontal movement of the print head to perform the printing operation. On the contrary, a spring acting against the actuator, besides giving to the user a similarity impression with the action exerted on a conventional mechanical stamper, serves to bring the print head back to its initial position.
It can be appreciated that in all the patents cited the relevant printing apparatuses do not allow a user to select with precision the zone on which he or she desires to print. Firstly, because it is the user who has to displace very approximately the printer, as he or she cannot see the zone to be printed underneath the printer. Secondly, because the user cannot reasonably estimate a travel of the print head to adjust the printing operation on the desired zone of the medium.
Thus, an object of the present invention is to make an electronic printer that functions exactly as a mechanical stamper in the way in which a print head is brought near to a medium to be printed.
Another object of the invention is to permit a precise printing on the desired zone of the medium independently of the precision of the operation of the user.
A further object of the invention is to allow a working position of the print head to be maintained independently of maintaining the force exerted by the user on the actuator until the printing operation is completed.
Yet another object of the invention is to permit the choice of the printing resolution that the user wants to obtain.
Another object of the invention is to allow the user to see the impression zone of the printer, i.e. the zone where the printing is performed, also when the printer is positioned in the printing zone.